Main precautions in the design of parts with strategic materials
Strategic metals such as precious metals and rare earths are present in small amounts in many applications including electronic components and printed circuit boards, the low-energy bulbs, catalytic converters for cars, etc. Overall Europe is heavily dependent on these resources from the rest of the world for the development of its technology. In the current programmed shortage, Europe seek to secure supplies by strengthening its policy of recycling of end of life goods and by controlling exports of waste containing these elements. She has published a list of strategic elements to be protected.
The deposit of waste containing these elements is now the subject of a new policy to exploit this « urban mine ».
The fact is that at global scale, only a small part of these strategic elements is recycled:
Without an adequate collection system and due to the complexity of product at end of life in terms of mixture of metals, it is estimated that much of the strategic metals have been buried for many years an almost irreversible. For example, 200 to 400 million tons of copper have been buried in landfills.
A global effort is to be done to all players in the industry. The role of designers will be to the extent possible:
- Avoid choosing components containing elements that become rare (and whose prices are likely to grow rapidly)
- Facilitate recycling, avoiding inconsistent associations. (see next section)
- Use of recycled metals
Association rules with strategic materials
The Metal-Wheel in figure below (Reuter and Van Schaik, 2012) illustrates as an example what happens to different metals in a PWB entering either the Iron (Fe), Aluminium (Al), Copper (Cu), Zinc (Zn) and Lead (Pb) processes. Each circle indicates the destination of a metal found in mixed, end-of-life electronic product (waste), while also reflecting a complete metallurgical processing sector in each Carrier metal section. This Metal Wheel shows the limits and opportunities of recycling which among others is the basis of rigorous systems DfRE tools as developed by Reuter and Van Schaik. It reveals the physics and thermodynamic details which have to be taken into account when performing Eco design.
The Metal-Wheel for recycling of a PWB, showing the destination of elements in the carrier metal processing infrastructures of each segment. Source: (M.A. Reuter and A. van Schaik (2012). Opportunities and Limits of WEEE Recycling – Recommendations to Product Design from a Recyclers Perspective. In: Proceedings of Electronics Goes Green 2012+, 9-12 September 2012, Berlin, Germany. In press. 8 p.)
For electronic boards, the recycling is often that of copper.
For example, we see that aluminium heat sink must be removed prior to the electronic board for recycling. The recycling of copper and electronic board is not reliable technically and economically for the recovery of aluminium. Aluminium will report to slag of the process, mixed with other residual metals and sent to landfill.
Example of heat sinks mounted on printed circuit boards
It is therefore necessary to facilitate the extraction (removal or sorting after grinding) of aluminium heat sinks or to design them with other metals, consistent with copper recycling process or with less environmental impact than aluminium and more easy to sort. A steel heat sink is cheaper to extract after grinding of the card (magnetic sorting) and steel production consumes fewer natural resources. At worst, if not removed, the steel will be found in slag and will be buried. The loss shall be less impact than the loss of aluminium.
Brass heat sink (Cu + Zn) will be completely recycled by this recycling process without the need for prior extraction. The use of recycled brass will be even more beneficial to the environment.
The composition of precious metals of many electronic components is now available at most producers:
Non exhaustive list of main producers of semiconductors
Take into account the limitations of current recycling processes
The current trend is the miniaturization of electronic components for many applications (mobile phones, microcomputers, …). However from a recycling point of view, the cards with tiny components are not very compatible with shredding and grinding operations of electronics goods or household appliances. Much of the components are snatched and are found in the final fraction that is not recycled (mineral fraction composed of glass, ceramics, metal dust and other impurities and plastic).
In practice, it would be necessary to remove the printed circuit boards before shredding / grinding products. This would have the advantage of better recycling precious metals and semi-precious (Silver, Copper, tin, …) and to avoid possible contamination by pollutant metals that can be found in the boards (lead in welding, …)
Reuter and van Schaik (2012) provide a qualitative overview of recycling/recovery possibilities for various critical materials in several types of WEEE based on physics and thermodynamics of recycling processes (see Table below) . This table illustrates the influence of choices that can be made about recycling routes, such as the degree of dismantling. Extensive dismantling of RE-containing dielectric components on printed wiring boards or of getters containing tungsten, cobalt, or tantalum from CRT televisions or lighting can recover materials that would otherwise be lost as contaminants to metal products or slag. A model, such as developed by Van Schaik and Reuter (2010), that is equipped with detailed material information allows users to assess different techniques. For example, the relative stability of oxides indicates that the REs form stable oxides that cannot generally be recovered by high-temperature means, but instead require hydrometallurgical processing. Table below also shows that the recovery of metals is ultimately dependent on their chemical properties, as metals with similar properties exhibit similar recoveries for various applications.
The recovery of different elements in the listed EoL products as a function of their processing route, showing that the recovery of metals is ultimately dependent on their chemical properties (Reuter and Van Schaik, 2012)
Case of rare earths and strategic metals
Studies in French and European level have recently highlighted the strategic importance of some metals for high-tech applications. These studies have compiled a list of 35 metals necessary for the development of high-technology applications used in Europe and whose are consider as « green » technologies: wind turbine, electric vehicles, compact fluorescent lamp, LED.
These metals are divided into three categories: platinoids, rare earths and others.
| Families | Metals studied | ||
|---|---|---|---|
| Platinoids | Platinum | Ruthenium | Rhodium |
| Palladium | Iridium | Osmium | |
| Rare earth elements | Lanthanum | Terbium | Yttrium |
| Cerium | Dysprosium | Gadolinium | |
| Praseodymium | Holmium | Scandium | |
| Neodymium | Erbium | Europium | |
| Promethium | Thulium | Lutetium | |
| Samarium | Ytterbium | ||
| Other metals | Cobalt | Gallium | Berylium |
| Titanium | Indium | Lithium | |
| Tungsten | Tantalum | Silver | |
| Rhenium | Germanium | Vanadium | |
Study: « étude du potentiel de recyclage de certains métaux rares » BIO IS for ADEME – 2010 – French
Current problems of Rare Earths Elements
At present the main problems related to rare earths is related to their supply. Global production of rare earths was estimated at 130 000 tonnes in 2010. However, 97% of this production is provided by China although it only has 37% of global reserves identified today (100 million tons). Moreover China limits the volume of its exports to 30,000 tons per year.
To cope with the risk of disruption of these resources three solutions are possible:
- The substitution of these metals by others: Unfortunately their special properties make them difficult to replace or with significant performance loss. In other cases it is at best possible to replace an element of the rare earth group by another.
- Optimization: Whether in manufacturing processes to reduce the amount of these metals to implement, or the use of these metals in a product. This is for example the case of Rhodia which as developed powder phosphors for LCD displays and compact fluorescent lamps that contain less terbium than current powders.
- Finally recycling: This solution is increasingly considered and promoted for several reasons. It enables direct bearing risk of disruption of these metals. In addition, it saves resources because for some elements (eg terbium) resources are expected to be depleted in few years. Finally, recycling is favoured by the presence of direct deposit in Europe at the heart of our waste including WEEE.
Relevance of recycling of rare earths and strategic metals in WEEE
The table below lists the applications containing rare metals for which recycling is particularly strategic
| Element | Li-ion Batteries | Magnets | Printed circuit boards | Capacitors | LCD Monitors | Compact fluorescent lamps | LED |
|---|---|---|---|---|---|---|---|
| Silver | X | ||||||
| Cerium | X | ||||||
| Cobalt | X | ||||||
| Dysprosium | X | ||||||
| Europium | X | ||||||
| Gadolinium | X | ||||||
| Gallium | X | X | |||||
| Germanium | X | ||||||
| Indium | X | ||||||
| Lanthanum | X | ||||||
| Lithium | X | ||||||
| Neodymium | X | ||||||
| Palladium | X | ||||||
| Platinum | X | ||||||
| Praseodymium | X | ||||||
| Tantalum | X | ||||||
| Terbium | X | X | |||||
| Yttrium | X |
Study: « étude du potentiel de recyclage de certains métaux rares » BIO IS for ADEME – 2010 – French
However, for other elements, recycling has so far not been considered relevant in view of their relative abundance (e.g. vanadium) or very limited number of applications (osmium, iridium, promethium, scandium, holmium, thulium, ytterbium and lutetium).
Recycling is even more relevant to prevents export of waste outside of Europe if they can be recycled, the activity can also generate employment. For example it is estimated that 17 tons of rare earth elements that could be recovered through 4000 tons of compact fluorescent lamps currently collected (15tons of yttrium, 1t of terbium and 1 ton of europium).
Status of recycling of rare earth elements and strategic metals
| State of recycling | Lithium-ion batteries | LED lamps | Magnets | Printed circuit boards | LCD Monitors |
|---|---|---|---|---|---|
| In France | Collection and recycling part of cobalt and lithium. | Collection but no treatment | Collection but no treatment | Collection and treatment, but no recycling of rare metals | Collection and treatment, but no recycling of rare metals |
| In the world | Recycling : Canada, Singapour, Sweden, Belgium, United States | LED circuit boards treated with | Recycling of production scrap (Japan) | Cards from France retired in Belgium, Germany, Sweden, Canada | Recovery of indium in Belgium and the United States |
| Research | Recycling of rechargeable batteries for electric vehicles (France) | Recovery of magnetic powders for new magnets (United Kingdom) | Recovery of precious metals (France) | Recycling projets indium (France, Japan, China) |
Study: « étude du potentiel de recyclage de certains métaux rares » BIO IS for ADEME – 2010 – French
Case of compact fluorescent lamps:
For compact fluorescent lamps the situation is somewhat different since the company Rhodia (Solvay group) is setting up a recycling program for six rare earths elements contained in compact fluorescent lamps (lanthanum, cerium, terbium, yttrium, europium and gadolinium). This operation is performed by two plants, the first is responsible for extracting rare earth elements from phosphor powders the second is responsible for their treatment.
For now, the company produces an industrial demonstrator so that the activity becomes operational in 2014.
Future prospects for recycling of rare earth elements
ADEME has identified main barriers to recycling of rare earths elements and precious metals. In return, the proposed actions to overcome these barriers revolve around the following four areas:
- « Acting upstream recycling chain »: Promoting eco-design to facilitate separation of components so that it can undergo a specific treatment (batteries, magnets). Involve producers to search for recycling solutions for products which may be specific and whose composition varies according to the producers (eg. LEDs).
- « Mobilizing waste deposit »: it could be envisaged to expand the scope of products collected but also to separate some products to treat them in specific manner (eg LCD)
- « Guiding and supporting R & D »: Improve available techniques and develop new technologies for the recycling of metals that do not yet have recycling techniques.
- « Activate recycling » with to two complementary methods: the obligation regulatory and financial incentives.
Synthesis
The use of precious metals is justified by the need for high performance properties for some applications such as components, catalysts, surface treatment …
Their cost is important, their use is optimized and quantities are minimized.
The design will therefore focus on:
- The substitution of rare elements by active elements less rare, or the potential use of recycled material less pure as the need permits;
- Materials that will gather associated with precious metals and rare earths, which are likely to hinder the recycling of these or be lost during the recycling of precious metals. (See: Association rules);
- An important accessibility and a quick removing of circuit boards found in electronic products and household in order to extract them before the grinding stage.
References
– M.A. Reuter and A. van Schaik (2012): Opportunities and Limits of recycling – A Dynamic-Model-Based Analysis, MRS Bulletin, 37(4), pp. 339-347.
– A. van Schaik and M.A. Reuter (2010): Dynamic modelling of E-waste recycling system performance based on product design. Minerals Engineering, Vol. 23, pp. 192-210.
– M.A. Reuter and A. van Schaik (2012). Opportunities and Limits of WEEE Recycling – Recommendations to Product Design from a Recyclers Perspective. In: Proceedings of Electronics Goes Green 2012+, 9-12 September 2012, Berlin, Germany. In press. 8 p.